Optical fiber connectors are a critical part of essentially all optical fiber communication systems. For instance, such connectors are used to join segments of fiber into longer lengths, to connect fiber to active devices, such as radiation sources, detectors and repeaters, and to connect fiber to passive devices, such as switches, multiplexers, and attenuators. The principal function of an optical fiber connector is to hold the fiber end such that the fiber's core is aligned with an optical pathway of the mating structure. This way, light from the fiber is optically coupled to the optical pathway.
Of particular interest herein are backplane connector systems. Backplane connector systems are well known, and typically comprise a substrate or a backplane on which are mounted one or more backplane connectors. A backplane connector is usually a receptacle and is configured to receive a connector plug. The plug connector typically comprises a ferrule that is biased forward with a spring to facilitate physical contact; however, the backplane connector in some industry standards does not have a biased ferrule to save space by avoiding the use of the spring. Space in backplane applications tends to be limited.
Although backplane connection systems tend to be robust and commercially popular, Applicant has discovered problems with respect to unacceptably high return loss (RL) caused by manufacturing anomalies typically found in multi-fiber ferrules, particularly with respect to variations in end face geometry and fiber protrusion. Specifically, referring to the schematic of a back-plane connector system 500 in FIG. 5, manufacturing anomalies, such as, for example, uneven polishing of the ferrule end face, cause an air gap 560 between the fibers 502 of the non-biased ferrule 501 and the forward-biased ferrule 503. (It should be understood that the unevenness of the polished end faces is exaggerated for illustrative purposes.) This problem appears unique to applications in which just one of the two mating ferrules is spring biased, as opposed to both ferrules being spring biased. Although the forward-biased ferrule may overcome some anomalies in ferrule end face/fiber protrusion configurations, if the manufacturing deviations are too extreme, proper optical coupling cannot be made between one or more of the fibers 502. Failure to make physical contact between the fibers is known to cause unacceptable RL and severely degrade the optical performance of the optical coupling.
Therefore, Applicant has discovered a need to accommodate manufacturing anomalies in a multi-fiber connector system. The present invention fulfills this need, among others.